AQA · GCSE · Chemistry

    Course version: 8462 · Version from Sept 2018

    In the United Kingdom (UK), rain provides water with low levels of…

    Full specification wording

    Potable water: In the United Kingdom (UK), rain provides water with low levels of dissolved substances (fresh water) that collects in the ground and in lakes and rivers, and most potable water is produced by: choosing an appropriate source of fresh water passing the water through filter beds sterilising.

    Potable water is water that is safe to drink, meaning it has sufficiently low levels of dissolved salts and microbes.

    Checked against the AQA 8462 specification (opens in a new tab) on .

    • Point 6 of 12
    • 3 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Potable water is water that is safe to drink, meaning it has sufficiently low levels of dissolved salts and microbes. In the UK, rainfall is naturally low in dissolved substances, so it is a useful fresh water source; it collects underground in aquifers and in lakes and rivers. To produce potable water, an appropriate fresh water source is first chosen, considering factors such as local availability, reliability of supply and the level of dissolved substances. The water is then passed through filter beds, which remove insoluble solids such as grit, soil and small particles. Finally it is sterilised to kill microbes. This sequence treats the water without removing all dissolved substances, because potable water is not pure water in the chemical sense.

    What earns the marks

    • Potable water is water that is safe to drink, with low levels of dissolved substances and microbes.
    • UK rain is naturally low in dissolved substances, so it is classed as fresh water.
    • Fresh water collects in the ground, including aquifers, and in lakes and rivers.
    • Choosing an appropriate source considers availability, reliability and the level of dissolved substances present.
    • Filter beds remove insoluble solids such as grit, soil and particles; they do not remove dissolved substances.
    • Sterilising kills microbes and is the final treatment step described for producing potable water.

    Common mistakes and how to put them right

    • Describing potable water as pure water.

      Put it right: Potable water still contains some dissolved substances, so the correction is to say it is safe to drink rather than chemically pure.

    • Claiming filter beds remove dissolved salts.

      Put it right: Filter beds remove insoluble solids, while dissolved substances remain.

    • Omitting the source-selection step and starting at filtration.

      Put it right: State that an appropriate fresh water source is chosen first.

    Exam tips

    • Link each treatment step to what it removes: filter beds remove insoluble solids, sterilising kills microbes.
    • Use the phrase low levels of dissolved substances when describing UK rain rather than saying it has no dissolved substances.
    • When asked to sequence the process, write the three stages in order: choose source, filter, sterilise.

    Try the lesson

    The start of the Potable water: In the United Kingdom (UK), rain provides water with low levels of dissolved substances (fresh water) that collects in the ground and in lakes and rivers, and most potable water is produced by: choosing an appropriate source of fresh water passing the water through filter beds sterilising. lesson, made from checked teaching notes for this specification point.

    Have a go first

    In the UK, which source of water is described as fresh water because it has low levels of dissolved substances?

    Listen

    Potable water is water that is safe to drink, meaning it has sufficiently low levels of dissolved salts and microbes. In the UK, rainfall is naturally low in dissolved substances, so it is a useful fresh water source; it collects underground in aquifers and in lakes and rivers. To produce potable water, an appropriate fresh water source is first chosen, considering factors such as local availability, reliability of supply and the level of dissolved substances. The water is then passed through filter beds, which remove insoluble solids such as grit, soil and small particles. Finally it is sterilised to kill microbes. This sequence treats the water without removing all dissolved substances, because potable water is not pure water in the chemical sense. A strong answer earns marks for these points. Potable water is water that is safe to drink, with low levels of dissolved substances and microbes. UK rain is naturally low in dissolved substances, so it is classed as fresh water. Fresh water collects in the ground, including aquifers, and in lakes and rivers. Choosing an appropriate source considers availability, reliability and the level of dissolved substances present. A common slip: Claiming filter beds remove dissolved salts. Instead, filter beds remove insoluble solids, while dissolved substances remain. Exam tip: Link each treatment step to what it removes: filter beds remove insoluble solids, sterilising kills microbes.

    See it

    A top-to-bottom flowchart. The first box says UK rain is fresh water with low levels of dissolved substances. An arrow leads to a box saying this water collects in the ground and in lakes and rivers. An arrow leads to a box saying choose an appropriate source of fresh water. An arrow leads to a box saying pass the water through filter beds. An arrow leads to a box saying sterilise. A final arrow leads to a box saying potable water.
    It shows how UK rain provides fresh water and the three stages used to produce most potable water: choosing a source, filtering and sterilising.

    Put it in order

    Put these steps in the order they happen.

    1. 1. Choose an appropriate source of fresh water
    2. 2. Collects in the ground and in lakes and rivers
    3. 3. UK rain: fresh water with low levels of dissolved substances
    4. 4. Potable water
    5. 5. Sterilise
    6. 6. Pass the water through filter beds

    Key words

    Say what each word means before you turn the card.

    Potable water

    Try answering aloud or in your head before turning the card.

    Filter beds

    Try answering aloud or in your head before turning the card.

    Sterilising

    Try answering aloud or in your head before turning the card.

    See every definition
    Potable water
    Water that is safe to drink, meaning it has sufficiently low levels of dissolved salts and microbes.
    Filter beds
    Passing the water through these removes insoluble solids such as grit, soil and small particles, but not dissolved substances.
    Sterilising
    The final treatment step described for producing potable water, which kills microbes.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-to-bottom flowchart. The first box says UK rain is fresh water with low levels of dissolved substances. An arrow leads to a box saying this water collects in the ground and in lakes and rivers. An arrow leads to a box saying choose an appropriate source of fresh water. An arrow leads to a box saying pass the water through filter beds. An arrow leads to a box saying sterilise. A final arrow leads to a box saying potable water.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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